const fs = require('fs');

const read_file = (fname, events) => {
  let noop = () => {};
  let onStat = events.onStat || noop;
  let onOpen = events.onOpen || noop;
  let onRead = events.onRead || noop;

  fs.stat(fname, (err, stats) => {
    onStat(stats);

    fs.open(fname, 'r', (err, fd) => {
      onOpen(fd);
      let inbuf = Buffer.alloc(stats.size);

      fs.read(fd, inbuf, 0, stats.size, null, (err, bytesRead, buffer) => {
        onRead(bytesRead, buffer);
      });
    });
  });
}

read_file('test.txt', {
  onRead: (bytesRead, buffer) => {
    console.log(`Read ${bytesRead} bytes: ${buffer.toString()}`);
  }, 
  onStat: (stat) => {
    console.log(`Got stats, file is ${stat.size} size.`);
  },
  onOpen: (fd) => {
    console.log(`Open worked, fd is ${fd}`);
  }
});